Simple chemicals trapped in clay, a seemingly infertile blend of minerals, for millions of years could react with each other in complex ways and give rise to biochemicals that are essential for life, Cornell University researchers found.

"We propose that in early geological history clay hydrogel provided a confinement function for biomolecules and biochemical reactions," said Dan Luo, professor of biological and environmental engineering.

In simulated ancient seawater, clay forms a hydrogel – a mass of microscopic spaces capable of soaking up liquids like a sponge.

Over billions of years, chemicals confined in those spaces could have carried out the complex reactions that formed proteins, DNA and eventually all the machinery that makes a living cell work.

Clay hydrogels could have confined and protected those chemical processes until the membrane that surrounds living cells developed. To test the idea, the Luo group demonstrated protein synthesis in a clay hydrogel.

Postdoctoral researcher Dayong Yang noticed that clay formed a hydrogel. It turned out unexpectedly that using clay enhanced protein production.

Researchers found what they had discovered might answer a long-standing question about how biomolecules evolved.

Scientists previously suggested that tiny balloons of fat or polymers might have served as precursors of cell membranes.

Clay is a promising possibility because biomolecules tend to attach to its surface, and theorists have shown that cytoplasm - the interior environment of a cell - behaves much like a hydrogel, researchers said.

Luo said that a clay hydrogel better protects its contents from damaging enzymes called "nucleases" that might dismantle DNA and other biomolecules.

Geological history shows that clay first appeared – as silicates leached from rocks - just at the time biomolecules began to form into protocells – cell-like structures, but incomplete – and eventually membrane-enclosed cells. The geological events matched nicely with biological events.